Mechanical oscillator chiefly for electronic timepieces



June 23, 1964 w BAUMGARTNER 3,137,992

MECHANICAL OSCILLATOR CHIEFLY FOR ELECTRONIC TIMEPIECES Filed March 9,1962 United States Patent 3,137,992 MECHANICAL OSCILLATOR CHIEFLY FORELECTRONIC TIMEPIECES Werner R. Baumgartner, Neuchatel, Switzerland,assignor to Laboratoire Suisse de Recherches Horlogeres, Neuchatel,Switzerland, a Swiss company Filed Mar. 9, 1962, Ser. No. 178,712

Claims priority, application Switzerland Mar. 14, 1961 1 Claim. (Cl.58-23) The regulating parts for time-pieces are generally constituted bya pendulum or a spiral balance spring oscillating at a comparatively lowfrequency and requiring a large amount of energy. Some electronicwatches are provided with a tuning fork of which the much higherfrequency may rise up to 500 cycles.

It has also been proposed to restort to arrangements oscillating at meanfrequencies ranging between about 30 and 60 cycles and including atorsion spring held fast at least at one of its ends and carrying a massadapted to rock round said spring. To this end, springs have been usedhitherto having different cross-sectional shapes such as that of acircle or of a cross. In this latter case, an excellent resistanceagainst bending is obtained but the machining and in particular thecutting of the cross-section is a delicate matter which is generally notsufiiciently accurate and leads to an objectionable internal straining.In order to cut out said drawbacks, it has already been proposed torestort to a system of springs constituted by several flat strips, theplanes of which meet one another along the oscillatory axis of the mass.This arrangement requires however the use of several blades and ofcomparatively intricate fitting systems and leads also to a difficultadjustment.

The present invention has for its object a mechanical oscillator,chiefly for electronic time-pieces, said oscillator including a torsionspring held fast at least at one of its ends and carrying a mass adaptedto rock round said spring. Said spring which does not show the abovementioned drawbacks, is constituted by a single blade of a generallyelongated shape extending perpendicularly to the axis of rotation of themass, said blade being bent throughout its length so as to showcross-sectionally the shape of a V.

The accompanying drawing illustrates by way of example an advantageousembodiment of my invention. In said drawings:

FIG. 1 is a general plan view of the arrangement,

FIGS. 2, 3 and 4 are partial cross-sections thereof, respectivelythrough lines II-II and III-III of FIG. 4,

FIG. is a wiring diagram of the electric movement maintaining system.

The oscillator illustrated includes a transverse arm 1 welded to atorsion spring element 2 secured at both ends to the plate 3 of atime-piece. Said arm 1 may of course be secured to the spring in variousways, for instance through gluing or mechanical securing. The springblade 2 has a constant thickness and a generally rectangularcross-section is bent so that its cross-section is in the shape of a Vor V-shaped throughout the length of the spring blade which extendsperpendicularly to the arm I. Said V-shaped cross-section may beobtained in a particularly easy manner and allows giving the finishedspring an excellent resistance against bending while retaining acomparatively reduced resistance against twisting. Experiments made haveshown that it is an easy matter to obtain a ratio equal to 7,500 betweenthe torsional and bending constants. The two ends of the arm 1 arefurthermore weighted each by the symmetrical masses 1a and 1b.

The two ends of the spring are each fitted rigidly in the plate 3 so asto define accurately the operative length of said spring. The fittingmeans include as shown in FIG. 3, on the one hand, a support 4 rigidwith the plate and provided with a V-shaped housing matching the shapeof the springs and furthermore, a bridge member 5 provided with adownwardly facing V-shaped projection 6. Screws 7 allow clamping thebridge member over its support 4. As a modification, it is also possibleto glue or else to weld the spring to the plate, for instance throughelectric or supersonic means.

The arm 1 is provided with a catch system which is not illustrated andwhich is adapted to drive a wheel 8 rigid with a worm 9. The lattercontrols the mechanism of the watch which mechanism includes anintermediate wheel 10, an eccentric seconds gear 11, a third gear 12 andlastly a center wheel 13. The motion work controlling the hands has notbeen illustrated.

The worm 9 allows shifting the plane of the mechanism and it is verysuitable for cooperation with time-setting means since it transmits themovements of the oscillator to the hands whereas, in the oppositedirection, it acts as a catch. The arm is constrained to oscillate underthe action of an electronic system including a control supply 14 feedinga transistor 15 in the control circuit of which is inserted a collectingwinding 16 while its power circuit includes a driving winding 17. Thetwo windings are carried by a U-shaped armature 18 provided at its outerend with a very narrow gap 19 facing one of the poles of the magneticbar 20. Said bar is carried inside a U-shaped magnetic member 21 whichis secured to the arm 1. The legs 22 of said member are separated fromthe bar 20 by a layer of non-magnetic material. When the magnet movestowards one end 18a of the armature, the flux produced by it induces inthe winding 16 a pulse which releases the transistor; the latter allowsthen current to pass through the winding 17 and the flux appearingconsequently inside the gap 19 urges the magnet into movement as thelatter moves thenafter towards the end 18b of the armature. Theoscillation of the whole arrangement has a frequency which may reach 30to 60 cycles and is extremely uniform.

What I claim is:

In a timepiece comprising a plate and a gear train, anelectro-mechanical oscillator for uniformly driving and regulating thedriving of said gear train, comprising an elongated torsion springelement twistable about its longitudinal axis, clamping means onopposite sides of said spring element securing opposite ends of saidspring element stationarily to said plate, said spring having a constantthickness and a V-shaped section along its full length intermediate saidsecuring means, an arm secured to said spring element intermediate saidopposite ends of said spring element and extending transversely of saidspring element and oscillatable about the longitudinal axis of saidspring element, said arm being secured across the open side of said V,means including an electronic circuit for oscillating said arm about thelongitudinal axis of sa d spring element and causing a torsionaltwisting of said spring element and means for imparting drive tosaidgear train from said oscillator during oscillatory motion thereof.

References Cited in the file of this patent UNITED STATES PATENTS 9,310Terry Oct. 5, 1852 1,541,138 Harje June 9, 1925 2,906,522 Wagner Sept.29, 1959

